1. Field of The Invention
The present invention relates to a structure of a rear window shelf portion of a vehicular body for partitioning a vehicular passenger compartment and a rear trunk in which a propagation of noise from the trunk to the passenger compartment can be prevented with a ventilating effect provided.
2. Description of Background Art
A Japanese Utility Model Registration First Publication No. show a 63-69652 published on May 11, 1988 exemplifies a previously proposed structure of a rear window shelf portion to partition the vehicular passenger compartment and rear trunk.
FIGS. 1 and 2 show another previously proposed structure of the rear window shelf portion generally similar to the disclosed structure of the rear window shelf portion in the above-identified Japanese Utility Model Registration Publication.
As shown in FIGS. 1 and 2, rear sound speakers 2 used for a vehicular audio system are mounted on a rear parcel (the term of the rear parcel is generally uncommon to United States of America and, hereinafter, referred to as a rear window shelf) panel 1 and ventilating openings 1a are formed at portions of the rear window shelf panel 1 which are located at rear ends thereof adjacent to a vehicular rear window (rear windshield). In addition, an opening 1b through which an operator accesses either a vehicular passenger compartment R or a rear trunk T in order to, for example, carry out electric wiring between the passenger compartment R and trunk T is formed at an intermediate portion of the rear shelf panel 1.
Furthermore, a rear shelf trim 4 is mounted on the rear window shelf panel 1 with a space provided against the rear shelf panel 1. Ventilating openings 4a whose position corresponds to the ventilating openings 1a of the rear window shelf panel 1, speaker openings 4b to radiate sounds derived from the speakers 2, and an opening 4c by which an air purifier (or air cleaner) is received are formed on the rear shelf trim 4. A plurality of felts 5a and 5b are attached on a rear side of the rear shelf trim 4 in order to improve a sound absorbing effect and a sound shielding effect.
In FIGS. 1 and 2, in addition to a ventilating path formed by the ventilating openings 1a of the rear window shelf panel 1 as a primary opening through which a ventilating air is passed to the trunk T and by the ventilating opening 4a of the rear shelf trim 4 as a secondary opening exposed to the passenger compartment R, other straight ventilating (air passages) paths formed by the ventilating openings 1a as the primary opening and by the speaker sound radiating openings 4b as the secondary opening are provided at the rear window shelf portion. Furthermore, still other ventilating paths (air passages) are formed between the opening 1b of the rear window shelf panel as the primary opening and the other openings 4b and 4c of the rear shelf trim 4 as the secondary opening. Hence, in the structure shown in FIGS. 1 and 2, an equivalent system to a Helmholtz resonator is established with the trunk T as a resonance chamber and the above-described paths and passages as a throat portion. Consequently, an equivalent cross sectional area of the throat portion is increased so that a resonance frequency of the resonator becomes high. Thus, the passenger compartment R is subject to receive a noise generated and propagated from the trunk T, particularly, low frequency components of the noise. Acoustic environment in the passenger compartment becomes unfavorable.